There are currently low pressure paint guns, such as those manufactured by Croix Air Products, Inc., which when new and clean, adequately provide for smooth application of paints, lacquers, and the like. Such paint guns use a low pressure to push liquid paint, lacquer, and the like through a metered valve outlet and into a nozzle through which pressurized air is flowing. The air mixes with, atomizes, and entrains the paint, and projects the mixture for deposit onto a surface to be painted, such as an automobile, or the like. When a paint job is completed, the paint gun system must be cleaned to avoid clogging. When the paint job is completed, the air pressure is stopped and liquid paint remains in the spray gun connector block. Unless a solvent is flowed through the gun immediately, a film of paint remains on the internal mechanism. As the existing paint connector blocks are composed of metal, this problem is particularly acute for paint designed to adhere to metallic surfaces For example, auto body paint can leave a substantial layer of paint adhered to the internal surfaces of the connector block. The dried paint can change the size of the internal metered orifices and adversely affect adjustment and the operation of the paint gun. If the layers are allowed to solidify between multiple jobs, or if the paint remains in the gun for a long time, a sufficient deposit can build up, such that the gun is completely inoperative.
It has been found that even when a solvent is forced through the gun barrel immediately after use, a cured layer of paint sometimes remains in the connector block which is not dissolvable with a short period of solvent. Cleaning usually requires disassembly of the gun and mechanical scraping or rubbing to dislodge the adhered and dried paint.